Neurochemical pathology in hippocampus in euthymic patients with bipolar I disorder

Objective: Subcortical regions such as hippocampus, thalamus and ventral putamen are assumed to be involved in the pathophysiology of mood regulation. Disturbed hippocampal neuronal function indicated by reduced N‐acetyl‐aspartate (NAA) levels in bipolar patients was shown by several studies. Results in thalamus and putamen are inconsistent. Method: N‐acetyl‐aspartate, choline (Cho), creatine (Cr) and myo‐inositol (Ins) were measured in left hippocampus, left thalamus and left putamen using proton magnetic resonance spectroscopy in 13 euthymic patients with bipolar I disorder and 13 pairwise matched healthy control subjects. Metabolic ratios NAA/Cr, NAA/Cho, Cho/Cr and Ins/Cr were calculated. Results: Patients with bipolar I disorder demonstrated significantly reduced NAA/Cr in the left hippocampus compared with healthy control subjects. No alterations were found in thalamus or putamen. Conclusion: We hypothesize that this NAA/Cr reduction might reflect neuronal dysfunction in the left hippocampus in patients with bipolar disorder.